1. Field of the Invention
This invention relates generally to gun-type power gas burners, and more particularly to an adjustable flame spreader for such burners.
2. Description of the Prior Art
Two types of gas burners are conventionally provided for firing domestic furnaces, i.e., atmospheric type and power type. Atmospheric burners rely entirely on atmospheric pressure for supplying combustion air to the burner, i.e., atmospheric burners do not incorporate a blower for supplying combustion air whereas, power burners include a blower. Many smaller, domestic hot water and steam furnaces designed for oil burner firing have a shallow combustion chamber and have boiler tubes extending upwardly which are supported by a crownsheet. There has been a trend in recent years to retrofit furnaces originally intended for oil burner firing with gas burners, however, most domestic furnaces originally intended for oil burner firing cannot be fired by a conventional atmospheric gas burner and thus, a power gas burner is required for such conversion.
Power gas burners inherently provide a long-narrow flame which is not suitable for use in a furnace having a shallow combustion chamber. Flame shapers or targets have been provided for atmospheric gas burners for providing the desired flame shape, such as those shown in U.S. Pat. Nos. 3,018,823; 3,077,517 and 2,905,235. However, such burners are of the type intended for converting coal-fired furnaces which have a large combustion chamber with the heat exchanger located thereover to gas and further, do not provide for adjustment of the flame shaping element after installation of the burner, i.e., the burner must be removed in order to adjust the flame shaping element.
The applicant's assignor has in the past manufactured atmospheric conversion gas burners having an angled, fixed target positioned in front of the burner primarily for deflecting the flame upwardly but which does provide some limited spreading of the flame. In common with other prior flame spreaders known to the present applicant, the target employed with that prior atmospheric burner was not adjustable after installation.
The applicant's assignor has also manufactured a gun-type power gas conversion burner having a fixed flame spreader.
Certain gun-type oil burners, such as those shown in U.S. Pat. Nos. 3,799,732; 3,225,813; 3,224,488 and 3,212,556, have employed a cone positioned in front of the blast tube, that shown in U.S. Pat. No. 3,225,813 being externally adjustable; however, the cone employed with a gun-type oil burner, while superficially resembling a gas burner flame spreader or shaper, is employed for an entirely different purpose, i.e., to provide proper mixing of the air and oil in order to secure proper combustion, the shape of the flame being developed by the nozzle angle rather than by the cone.
The combustion chambers of smaller, domestic hot air and steam furnaces originally designed for oil burner firing have a variety of sizes and configurations, i.e., round, square or rectangular and thus, in converting such furnaces to power gas burner firing, it is necessary properly to size and shape the flame for the particular combustion chamber. Therefore, in providing a gun-type power conversion gas burner suitable for use with a wide variety of such furnaces, it is desirable to provide an externally adjustable flame spreader so that the installer can properly size and shape the gas flame to fit the combustion chamber after the burner is installed without the necessity for removing the burner.